From Event: SPIE Nanoscience + Engineering, 2019
Spin-orbitronics, which takes advantage of spin-orbit coupling (SOC), has expanded the research objects of spintronics to nonmagnetic materials. Here, we report the emerging nonlinear spintronic phenomena in the inversion-asymmetric nonmagnetic materials with SOC. For instance, the surface state of three-dimensional topological insulator (TI) owns helical spin textures with the spin and momentum perpendicularly locked. We show the observation of a nonlinear magnetoresistance (called bilinear magneto-electric resistance, BMER) and nonlinear Hall effect in a prototypical TI Bi2Se3, which scale linearly with both the applied electric and magnetic fields. We further reveal that these effects are originated from the conversion of a nonlinear spin current to charge current under the application of an external magnetic field. A close link between the BMER and the spin texture was established in TI surface states, which enables a novel transport probe of spin textures. We further extended the observation of BMER effect to the d-orbital two-dimensional electron gas (2DEG) at a SrTiO3 (STO) (111) surface. The BMER probes a three-fold out-of-plane spin texture, in addition to an in-plane one at the STO(111) surface 2DEG. This novel spin texture is in contrast to the conventional one induced by the Rashba effect. By performing tight-binding supercell calculations, we find that this 3D spin texture is fully described by the confinement effects of the STO t2g conduction band in the (111) plane. These findings open a new branch in spintronics, which discusses the nonlinear transport effects in spin-polarized nonmagnetic materials, and is therefore referred to as nonlinear spintronics.
© (2019) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Pan He, Shulei Zhang, Siobhan McKeown Walker, Dapeng Zhu, Olle Heinonen, Felix Baumberger, Giovanni Vignale, and Hyunsoo Yang, "Nonlinear spintronics in nonmagnetic materials with inversion symmetry breaking (Conference Presentation)," Proc. SPIE 11090, Spintronics XII, 110901U (Presented at SPIE Nanoscience + Engineering: August 13, 2019; Published: 10 September 2019); https://doi.org/10.1117/12.2528393.6083795922001.